Odontogenic Tumours Classification

Classification of Odontogenic Tumours

• Based on cell of origin:
  • Tumours of Odontogenic Epithelium (dental lamina + enamel organ)
  • Mixed Tumours (odontogenic epithelium + ectomesenchymal tissue with or without dental hard tissues)
  • Tumours of Ectomesenchymal Tissue (cells of the dental papilla)

Odontogenic Tumours - General Rules

• Very uncommon
• Generally benign, although some may exhibit aggressive behaviours
• Malignant odontogenic tumours are extremely rare

Clinical Presentation

• Ranges from incidental finding to an asymptomatic expansile mass
• Can present as unilocular or multilocular lesions
• May or may not be associated with a tooth

Odontogenic Epithelium Tumours (benign)

• Ameloblastoma
  • Conventional, Unicystic, Extra-osseous/Peripheral, or Metastasizing
• Adenomatoid Odontogenic Tumour (AOT)
• Calcifying epithelial odontogenic tumour (rare)
• Squamous odontogenic tumour (rare)

Ameloblastoma

• Benign tumour of odontogenic epithelium
• Huge growth potential and infiltrative growth pattern
• High recurrence rate if simply curetted
• Can extend into base of the brain and cause death if left untreated

Clinicopathologic Types of Ameloblastoma

• Conventional
• Unicystic
• Peripheral
• Metastasizing (very rare)

Epidemiology of Ameloblastoma

• Rare under the age of 10
• Uncommon in 10-19 years old
• Equal prevalence in 3rd to 7th decade
• 80-85% occur in the mandible (usually posterior)

Clinical Presentation of Ameloblastoma

• Painless swelling or expansion
• Capable of significant growth if left untreated
• Pain and paresthesia are uncommon

Radiographic Presentation of Ameloblastoma

• Multilocular radiolucency (soap bubble or honeycomb appearance)
• Expansile lesion with thinning of the cortices
• Found in any relation to the teeth or with no adjacent tooth
• Radiographic margins range from well- to ill-defined, but usually somewhat defined
• Root resorption is common

Histopathology of Ameloblastoma

• Hyperchromatic nuclei of ameloblast-like basal epithelium
• Stellate reticulum-like cells
• Some discrete keratin formation in the middle
• An ameloblastoma island is like an inverted dental organ, with the ameloblastoma-like cells on the periphery

Unicystic Ameloblastoma

• Cystic tumour lined by odontogenic epithelium with a low recurrence rate
• Tend to present in the second decade most commonly
• 90% in mandible – predilection for the posterior
• Clinical and Radiographic Presentation: Unilocular, pericoronal radiolucency

Variants of Unicystic Ameloblastoma

• Intraluminal
  • Papillary appearance to the lumen of the tumour (gross appearance)
  • Plexiform growth pattern in the odontogenic epithelium
• Luminal
  • Mural

Management and Prognosis of Ameloblastomas

• Conventional (conventional and mural)
  • 5-17% recurrence rate with resection
  • 30-35% with curettage or enucleation
• Unicystic (luminal and intraluminal)
  • 6-37% recurrence
• Peripheral ameloblastoma
  • No recurrence with simple excision

Adenomatoid Odontogenic Tumour (AOT)

• Definition: Uncommon benign tumour of odontogenic epithelium
• Epidemiology: Teenagers – rarely over age 30, strong female predilection (2:1), loves the maxilla (2:1)
• Clinical Presentation:
  • 2/3 adolescents
  • 2/3 females
  • 2/3 maxilla
  • 2/3 associated with unerupted root
• Radiographic: Initially radiolucent, then flocculent opacities (“snowflakes”)
• Treatment: Encapsulated – thus enucleates cleanly on curettage, when a tooth is involved, the tooth is extracted, rarely recurs

Calcifying Epithelial Odontogenic Tumour (CEOT)

• Definition: Benign, aggressive neoplasm of stellate intermedium and/or reticulum
• Less aggressive than ameloblastoma
• Epidemiology and Clinical Presentation: Rare, most common presenting sign is a painless, slow-growing swelling
• Radiographic Presentation: Unilocular (more in maxilla) or multi-locular, margins are typically scalloped and well-defined; may be corticated or ill-defined
• Histopathology: Clusters of polyhedral epithelial cells, often intercellular bridges, large and dysplastic-looking cells, background fibrous stroma